The present invention relates to a mechanical pencil having an internal mechanism with its distal end movable into and out of an opening in a distal end of a pencil barrel in response to a larger push, wherein a lead can be projected in response to a smaller push under a writing condition in which the distal end of the internal mechanism projects out of the opening in the pencil barrel.
There have already been proposed mechanical pencils in which the distal end of an internal mechanism is moved in and out by a larger push and a lead is projected by a smaller push, as disclosed in U.S. Pat. No. 3,724,960, Japanese Patent Publication No. 14524/79 and Japanese Utility Model Publications Nos. 34328/76 and 34329/76. These known mechanical pencils have a cam mechanism disposed on an outer circumferential surface of a lead casing for taking the distal end of the internal mechanism into and out of the opening in the distal end of the pencil barrel. The lead casing is considerably large in diameter so as to be able to contain a multiplicity of leads. With the cam mechanism disposed around the thick lead casing, the pencil barrel having a cam wall aligned with the cam mechanism must also be large in diameter. This has been an obstacle to attempts to achieve mechanical pencils of smaller diameter. In the known mechanical pencils, the cam mechanism is integral with a rear pencil barrel. It is frequent practice in the mechanical pencil industry for manufacturers to buy and sell their products among themselves. For example, many makers purchase only internal mechanisms from other makers, assemble them into pencil barrels of their own, and sell completed products under their own brands.
It is desirable that one manufacturer fabricate a quantity of versatile internal mechanisms and sell them to a plurality of companies of writing instruments, and the companies assemble the purchased internal mechanisms into pencil barrels of their own for sale under their own brand names. Since such a way of business allows the manufacturer to mass-produce internal mechanisms of one type, the cost of production can be reduced and the internal mechanisms can be sold to other makers at reduced prices. The companies of writing tools then can put purchased mechanisms into their own barrels, so that they can sell the products under their own names to their advantage. Therefore, the consumers can buy completed mechanical pencils at reasonable prices. The foregoing practice is considered totally as a good production and selling system to provide benefits to all of the internal mechanism manufacturer, the assembling makers, and the consumers. However, since the cam mechanism has heretofore been formed integrally with the rear pencil barrel, it has been impossible for one manufacturer to sell only internal mechanisms to other makers.